Rotary bit for dry rock drilling



June 19, 1956 B. D. SMITH 2,751,196 ROTARY BIT FOR DRY ROCK DRILLINGFiled April 22, 1955 2 Sheets-Shea t l 2&

INVENTOR ,Be Zmonzfl. Smith,

ATTO E Y June 19, 1956 B. D. SMITH 2,751,196

ROTARY BIT FOR DRY ROCK DRILLING Filed April 22, 1955 2 Sheets-Sheet 2 7.33 a I 29 i 1 3/ 0 l0 1 22 1 I l/ 20 .2

INVENTOR 2,751,196 ROTARY BIT FOR DRY RGQK DLING Belmont Duard Smith,Eaton, Ohio Application April 22, 1955, Serial No. 503,292 Claims. (Cl.255-304) This invention relates to rotary rock drilling apparatus, andhas for its principal object the provision of an improved drill bit ofthe rotating cutter type which is especially adapted for use in the drydrilling of rock formations, as for example, in the production ofblasting holes in quarrying operations.

The use of rotary cutter bits in the drilling of oil, gas and other deepwells is well known and in such operations the common practice is tocool the cutters and bring the cuttings to the ground surface by meansof a flushing liquid or semi-liquidv slush or mud which is pumped downthrough the drill stem, discharged over or around the cutters, andreturned to the surface along with the cuttings through the bore'exteriorly of the stem. The bearings upon which the cutters rotate areprotected as well as possible against entry of the cuttings thereto, andin at least some instances provision has been made for supplying alubricant to them.

In some fields, as in quarrying, the presence of liquid in the bore holeis objectionable and therefore it has been proposed to modify theconventional. oil well practice by using compressed air rather thanwater or slush as the cooling and flushing fluid. This is feasible sincein such operations the bores ordinarily do not extend to depths greaterthan a few hundred feet and air pressures on the order of from 25 to 100pounds per square inch are sufficient to bring the cuttings to thesurface. In some bits employed in such work, in addition to dischargingthe air over or around the cutters, the bit has been providedwith ductswhereby a portion of the air may be discharged directly to the cutterbearings for cooling purposes.

The bit of the present invention is basically one of this type. However,it is provided with means whereby a pool. of oil or analogous lubricantmay be established within the bit in such position as to be directlyactediuporr by the compressed air and thereby constantly forced to: thecutter bearings through the conventional air cooling ducts. Theconstruction is suchthat the lubricant in the pool can be replenishedwithout withdrawing the bit from the bore; for example, as the drillingproceeds before each length of drill stem is added to the string. asmall quantity of oil is merely poured into the stem already in the holeand descends along the stern wall by gravity to the pool in the bit.Thus, an adequate supply of lubricant for the cutter-bearings may bemaintained with a minimum expenditure of time and effort.

In another aspect of the invention the means for establishing thelubricant pool comprises a tubular member or thimble disposed in themain air passage of the bit body and having a plurality of ports in itslower end for directing jets of air between the rotary cutters, theupper end portion of said thimble projecting upwardly from said main airpassage and in conjunction with the peripheral Wall of the bit providinga reservoir in whichthe lubricant pool is established and maintained,and from which the lubricating ducts lead to the cutter bearings. Thethimbles may be merely frictionally retained in the bit passage wherebyto be readily changeable to 2,751,196 Patented June 19,1956

meet varied operating requirements, or in some instances they'ma'y bepermanently securedin place as by welding them to the bit body.

Several embodiments of theinvention are illustrated in the accompanyingdrawings constituting a part of this specification, in: which like.reference characters designate like parts throughout. the views and inwhich:

Figure 1 is a' central vertical sectional view of a rotarycutterrockdrilling bit embodying one form of the invention;

Fig. 2' is a horizontal"sectional-plan view on the plane indicated bytheline 22'in Fig. 1;

Fig. 3 is a fragmentary view similar to Fig. 1 but on a somewhat smallerscale, showing a slightly different form of bit and thimble;

Fig. 4 is a fragmentary view similar to Fig. 3, showing a longer thimblepermanently secured inplace;

Fig. 5 is a similar view showing formation of the lubricant reservoir bymeans of an integral annular flange extending upwardly from the bit bodyaround the air passage;

Fig. 6 is a similar view illustrating application of the invention to abit having a plurality of air passages through its body; and

Fig 7 is a perspective view of astill further modified form of jet and.reservoir forming element- Referringrmore.particularly to Figs. 1 and 2,the rotaryeutter bitll) there shown comprises a body 11 having the usualtubular thre'aded extension 12 for attachment. to the drilling stem(not; shown). A. plurality of circumferentially spacedlcgs 13 dependfrom the body 11, each of which is provided. with an inwardly extendingconiform boss 14-upon which a toothed cutter element or cone 15 isrotatably mounted by means of. antifriction balls and/ or rollers 16 and17. Each coniform boss 14 is provided with ducts 18" and'19: whichcommunicate with a duct 20 that extends upwardly through the leg 13 andbody 11 to the peripheral portion of the chamber 21 provided by thetubular threaded extension of the bit. The said ducts have heretoforeserved to conduct a portion of the compressed air supplied tothe chamber21 to the cutter bearings 16 and: 17 whereby to cool them; and the body11 has been provided with. an axial passage 22 through which the majorportion of the. air has been discharged over. and around the cutters15-.

While the supplying of air to the cutter bearings may cool them to someextent, the small clearances through which the air must pass. are notconducive to a flow adequate to satisfactorily perform the intendedpurpose, and in many instances it has been found insufficient to preventheating and expansion of the parts with resultant seizing or locking ofthe cutters. Neither does the air prevent wear incident to themetal-to-metal contact of the parts, and all in all the life of thebearings of these prior bits has been relatively short.

To overcome this, in the form of the present invention shown. in Figs. 1and 2 there is removably disposed in the main air'passage 22' of the bitbody a thimble member 25- the'lower closed end of which is locatedsomewhat below the plane of the under face of the body 11' and isprovided with a plurality of inclined radially extending" air passages26. These are of reduced diameter as compared with that of the bore 27of the thimble, with which they communicate, and they are so disposed asto. direct jets of air from the chamber 21 outwardly and downwardly intothe rock bore, preferably between the cutters 15.

The flaring, upper portion 28 of the thimble member extends upwardlyinto the bit chamber 21 substantially as shown in- Fig 1 and inconjunction with the peripheral wall andbottom. of said chamber providesan annular open-toppedreservoir 29-: in which a pool of oil or similarlubricant 30 may be established and replenished as necessary by merelypouring such lubricant in to the upper end of the drill stem, withoutwithdrawing the drill from the hole. The top surface of the pool isindirect contact with and subject to the pressure of the air supplied tothe chamber 21, whereby a forced feed of the lubricant through the ducts20, 19 and 18' to the cutter bearings is maintained, thus insuring freerotation of the cutters and lengthened life of the bearings.

The bit shown in Fig. 3 differs slightly from that of Fig. 1 in that theduct 20' instead of communicating with ducts such as 18 and 19 in thebearing boss 14, discharges directly into the clearance between thecutter and said boss. The tubular member 31 shown in Fig. 3 also isslightly different, being tapered throughout its length, and while itsupper portion projects into the bit chamber 21 whereby to provide thelubricant reservoir 29 as in the preceding form, its lower end isdisposed approximately in the plane of the under face of the body 11.The jet passages 26 also are of relatively smaller diameter than thoseof Fig. l.

The thimble shown in Fig. 4 is similar to that of Fig. 3 except that itis longer whereby to extend further below the under face of the bit bodythan either of the forms shown in Figs. 1 and 3, and in addition to theradial jet passages 26 it is provided with an axial passage 26'. Thisthimble is also indicated as being rigidly secured in place by weldingit to the body 11 at 32. It will be obvious from Figs. 1, 3 and 4 thatthe thimbles may be of varying lengths whereby to discharge the aircloser to or farther away from the cutters 15, and that the diametersand arrangements of the jet passages may be varied as necessary ordesired to meet various operating conditions. Thus, since the thimblesare readily interchangeable the bits are easily adaptable to various airpressures and to any drilling situations that may be encountered whileat the same time retaining the advantageous mode of lubricating thecutter bearings.

In lieu of employing the thimbles or 31 to provide the lubricantreservoir 29, the same result may be attained by means of an annularflange extending upwardly from the body 11 into the bit chamber 21, asshown in Fig. 5.

Some bits, instead of having a single axial air passage 22, are providedwith a plurality of smaller passages as shown at 34 in Fig. 6. If thesebe located sufiiciently close to one another the bit body may be boredout to provide a single axial passage and a thimble inserted therein asin Figs. 1, 3 and 4. If however, the passages 34 are too widely spacedto make this feasible, a tubular nipple 35 may be removably or rigidlydisposed in each such passage, as shown in said Fig. 6, whereby toprovide the oil reservoir 29.

In Fig. 7 there is illustrated a plug member 36 provided with aplurality of air passages 37 extending through it longitudinally, whichmay be used in place of the thimbles shown in Figs. 1, 3 and 4.

is added to the string, without withdrawing the bit from the hole as ispossible with the present invention, the life of said bearings mayeasily 'be lengthened by from 100% to 200% over that of unlubricated ormere air-cooled bearings, and thus it is economically feasible to re-tipthe cutter teeth two or three times.

Having described several exemplifications of the invention, what isclaimed is:

1. A rotary bit for dry rock drilling, comprising a bit body having achamber in its upper portion for receiving compressed air, and aplurality of cutter elements rotatably carried by its lower portion, thebody also being provided with an air passage extending from the chamberto adjacent said cutter elements, and with ducts extending from thechamber to the bearings of the cutter elements; and means extendingupwardly from said air passage into the body chamber and in conjunctionwith portions of the walls of the latter providing an opentoppedreservoir adapted to receive lubricant poured into the top of thechamber and thereby provide a lubricant pool the surface of which issubject to direct action of the compressed air in the chamber wherebysuch lubricant may be forced through said body ducts to the bearings ofthe cutter elements.

2. A rotary bit for dry rock drilling, comprising a bit body having achamber in its upper portion for receiving compressed air, and aplurality of cutter elements rotatably carried by its lower portion, thebody also being provided with an air passage extending from the chamberto adjacent said cutter elements, and with ducts extending from thechamber to the bearings of the cutter elements; and an air conductingmember disposed in said body passage and projecting from the upper endthereof into said chamber in wholly spaced relation to the walls of thelatter whereby to form, in conjunction with portions of said chamberwalls, an open-topped reservoir 7 adapted to receive lubricant pouredinto the top of the chamber and thereby provide a pool of lubricantwhich is subject to direct action of the compressed air in the chamberwhereby such lubricant may be forced through said body ducts to thebearings of the cutter elements.

3. A rotary bit for dry rock drilling, comprising a bit body having achamber in its upper portion for receiving compressed air, and aplurality of cutter elements rotatably carried by its lower portion, thebody also being provided with an axial air passage extending from thechamber to adjacent said cutter elements, and with ducts extending fromthe lower peripheral portion of the chamber to the bearings of thecutter elements; and a tubular air conducting member readily removablydisposed in said body passage With its upper portion extending into saidchamber whereby, in conjunction with portions of Although the cutters 15are formed of hardened alloy steel, wear on the cutter teeth unavoidablytakes place during use or" the bits and they become shortened andblunted or rounded to such an extent as to materially impair theircutting efliciency. When this occurs it is an accepted practice in theart, if the cutter bearings be still serviceable, to rebuild the teethwith weld metal to substantially their original size and shape, as thiscan be done at a cost appreciably less than that of a new cutter. It hasbeen found however, that where adequate lubrication of the cutterbearings has not been provided, such bearings usually are so badly wornby the time the cutter teeth need re-building that repair of said teethis uneconomic since the worn bearings will fail rapidly once the bit isput back into service.

By making proper lubrication of the cutter bearings a mere matter ofpouring a half pint or so of oil into the upper end of the drill sterneach time a length of stem the walls of the latter, to form an annularopen-topped reservoir adapted to receive lubricant poured into the topof the chamber and thus provide a pool of lubricant the surface of whichis subject to direct action of the compressed air in the chamber wherebysuch lubricant may be forced through said body ducts to the bearings ofthe cutter elements.

4. A rotary bit for dry rock drilling, comprising a bit body having achamber in its upper portion for receiving compressed air, and aplurality of cutter elements rotatably carried by its lower portion, thebody also being provided with an air passage extending from the chamberto adjacent said cutter elements, and with ducts extending from thechamber to the bearings of the cutter elements; and an annular flangeconcentric with said body passage and extending upwardly therefrom intosaid chamber and in conjunction with portions of the chamber wallsproviding an open-topped reservoir adapted to receive lubricant pouredinto the top of theehamber and thus provide a pool of such lubricant thesurface of which is subject to direct pressure of the air in the chamberwhereby said lubricant may be forced through said body ducts to thebearings of the cutter elements.

5. A rotary bit for dry roc i drilling, comprising a bit body having achamber in its upper portion for receiving compressed air, and aplurality of cutter elements rotatably carried by its lower portion, thebody also being provided with an air passage extending from the chamberto adjacent said cutter elements, and with ducts extending from thechamber to the bearings of the cutter elements; and an elongated plugmember provided with air passages extending longitudinally therethrough,said plug being disposed in said body air passage with its upper endportion projecting therefrom into the body chamber and in conjunctionwith portions of the chamber walls providing an open-topped reservoiradapted to receive lubricant poured into the top of the chamber and thusprovide a pool of such lubricant the surface of which is subject todirect pressure of the air in the chamber whereby said lubricant may beforced through said body ducts to the bearings of the cutter elements.

References Cited in the file of this patent UNITED STATES PATENTS1,708,288 Wadsworth Apr. 9, 1929 1,816,203 Behnke July 28, 19312,661,932 Woods Dec. 8, 1953

